Gordon Tollin

Regents Professor Emeritus - Retired

Degrees and Appointments

Ph.D. 1956, Iowa State University

The transduction of information across biological membranes is one of the key processes in living systems. In many cases, such signals are transmitted via a class of integral membrane proteins known as G-protein coupled receptors (GPCRs). These are ubiquitous in eukaryotes and constitute one of the primary targets for pharmaceuticals. We have developed a new spectroscopic tool, called plasmon-waveguide resonance, that allows one to monitor conformational changes in real time in a single lipid bilayer occurring as a consequence of the functional activity of membrane proteins, without the use of labels of any kind. We are applying this to a variety of membrane systems, including GPCRs such as the delta opioid receptor, the beta-2-adrenergic receptor, the cannabinoid receptor and rhodopsin, and ion channels such as the nicotinic acetylcholine receptor.

Electron transfer processes play key roles in a wide variety of basic biological phenomena: e.g., respiration, photosynthesis, nitrogen fixation, steroid and DNA biogenesis, fatty acid and carbohydrate catabolism, etc. These reactions involve redox proteins consisting of one or more polypeptide chains, which bind cofactors such as metal ions (copper, iron-sulfur clusters) and metallo-organic (heme) or organic (flavin) molecules which function as electron or hydrogen carriers. Redox proteins may be soluble or membrane-associated, and electron transfer can occur via both inter- and intra-protein reactions. The primary goals of our research programs are to elucidate the relationships between redox protein structure and the biochemical specificity, the rates and the mechanisms of these reactions, and to understand the role of lipid bilayer membranes in controlling and modulating redox protein properties. The tools which we use include transient-state kinetic methods such as stopped- flow and laser flash photolysis spectrophotometry, optical spectroscopic (including surface plasmon resonance) and electro-chemical methods, site-directed mutagenesis and computer molecular graphics.